<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>demo3</title>
    <style type="text/css">
        .a{
            color: red
        }     
        .b{
            color: blue
        }
    </style>
</head>
<body>
    <p class="b a">sdfasdf</p>
</body>
</html>